Production fluids which include oil, water, gas, and entrained sand from a well penetrating a hydrocarbon formation must be separated into separate components for transportation from the production site or in the case of sand and water for disposal. When production is obtained on an offshore structure, special problems are encountered because of the limited space available for process equipment. This is especially true when the production fluids include low API gravity oil (for example, less than 25 API). This type of heavy oil is viscous and relatively dense. Also when production is offshore, the oil usually arrives at the platform cold. Handling process fluids, including dense viscous cold oil, requires large processing equipment thus reducing the viability of many heavy oil field developments particularly in the offshore environment. Many techniques have been suggested for handling production fluids in such circumstances but none have been entirely satisfactory.